PERRIN_Jeff
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- Joined
- Apr 19, 2018
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- 31
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- Location
- Hillsboro, Oregon
- Vehicle(s)
- 2017 Civic Si Coupe
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- #1
ACT Sensor Issue/Mod
During some recent testing of our FMIC and oil cooler kit, we noticed how the ACT (Air Charge Temp) sensor was reading extremely high (170F) after the run was over. After the normal cool down time it continued to read 150F for a few minutes. This is during a time that the charge temps should have recovered, and it should be reading closer to 100F. Even holding the RPM at 3000RPM didn’t cause the sensor to change much. After some investigating, we found something that every CRT owner should be aware of.
What is this ACT sensor and where is it?
Tuning software refers to this sensor as IAT (Intake Air Temp), which is a bit confusing as it is not the air temp sensor located in your intake system (part of the MAF sensor). Typically, IAT is used for the temperature reading at the intake, and Air Charge Temp/Intake Manifold Temp (ACT) is what is used to describe the air temp entering the engine. With that said, I am going to refer to this as the ACT sensor, as this is better term to describe it.
The Air Charge Temp sensor (ACT) is a located in the TMAP sensor bolted to the intake manifold. The TMAP sensor is a temperate and manifold pressure sensor in one and is very commonly used on modern turbo engines. The air temp sensor portion of this is the small bulb/teardrop thing hanging off the side of the sensor (called a thermistor). The flaw I found was that the actual sensor is laying up against the plastic housing of the TMAP sensor body (verified our other shop car has the same issue) and it is shrouded by plastic fins.
This is bad because the intake manifold and sensor housing heat up to that 170F (sometimes hotter) and that heat gets transferred into the sensor. Even if the actual air temp is 100F, the sensor will be affected from touching something that is much hotter. Add the fact that plastic maintains heat for a long period of time, and you get very inaccurate readings. Going further, add the typical oil from blow by that accumulates on the sensor and it transfers even more heat. It does make for very consistent readings, but they are not a representative of what the actual air temp entering the engine is. This was verified by using the data we get from KTuner and using a laser temp probe to measure the surface of the sensor and the intake manifold. All of which read the same temp after the run was over and after the cool down.
An example is after a dyno run, we were seeing 150F ACT reading on the software, and with the laser probe. Revving up the motor to 4000RPM showed the temp hover around 145F, when this should have shown more like 100F. I saw the problem, only question is, can it be fixed and will it even do anything?
The Fix/How-To
I set off to fix this by trimming off the shroud in the center of the sensor. In the picture above you can see i outline the small center rectangle showing the center shroud. I used an X-acto knife and very carefully sliced it off as far down as I could. Then using a small flathead screw driver I bent the probe carefully toward the middle until it no longer touches anything (You will need to push it from part way down the probe as it will just spring back if you push from the top of it). After it was all done, the sensor was resting in the air not touching anything and still protected by some of the plastic housing. This took a whole 5 minutes of work with an X-acto knife. Below is what it looks like after it has been modified.
Results
Does fixing this actually do anything? Absolutely! First and foremost, there was an increase in power! Since the ECU uses charge temps and intake temps to control torque (boost and other things) it actually added power! Just to give you some idea, we were seeing consistently 300WHP before this mod (OEM intercooler, 3” Catback with overpipe, and Ktuner). After the fix, the HP jumped up 20WHP, and we saw the air temp recovery time change much faster and our laser probe measured the same 150-160F on the sensor and manifold, while the ECU was seeing 130F. Only downside was now that the ECU was reading a more accurate temperatures, we were now seeing a fluctuation in power. See the below graph showing the grouping of the runs.
It is hard to see but before the mod the HP was consistently low (grouping within smaller circle). After the mod the HP jumped up and stayed up a bit longer, but eventually did fall down to about 300WHP. Keep in mind that these tests were done on our dyno where things are very consistent, and we don’t have fans that can replicate road speed. This tends to lean to slightly worse conditions where there isn’t the same cooling as found on the street. Our testing methods can get close to track like conditions as we can replicate the same higher coolant temps people see on the track, but don’t see on the road.
And all dyno runs we have shown and will show, will be done with this ACT mod. I think it’s important for the consistency and accuracy of data.
The question is, does your car have this same problem? Does this apply to all the non-Type-R turbo models? We are not 100% sure at this point, but since we have now seen this on 4 cars, my guess is most Type-R’s have this issue. I would love to hear from people and see if their sensor is the same way.
WARNING: There is some added risk that this mod could cause the sensor to fail. Please mod at your own risk!
During some recent testing of our FMIC and oil cooler kit, we noticed how the ACT (Air Charge Temp) sensor was reading extremely high (170F) after the run was over. After the normal cool down time it continued to read 150F for a few minutes. This is during a time that the charge temps should have recovered, and it should be reading closer to 100F. Even holding the RPM at 3000RPM didn’t cause the sensor to change much. After some investigating, we found something that every CRT owner should be aware of.
What is this ACT sensor and where is it?
Tuning software refers to this sensor as IAT (Intake Air Temp), which is a bit confusing as it is not the air temp sensor located in your intake system (part of the MAF sensor). Typically, IAT is used for the temperature reading at the intake, and Air Charge Temp/Intake Manifold Temp (ACT) is what is used to describe the air temp entering the engine. With that said, I am going to refer to this as the ACT sensor, as this is better term to describe it.
The Air Charge Temp sensor (ACT) is a located in the TMAP sensor bolted to the intake manifold. The TMAP sensor is a temperate and manifold pressure sensor in one and is very commonly used on modern turbo engines. The air temp sensor portion of this is the small bulb/teardrop thing hanging off the side of the sensor (called a thermistor). The flaw I found was that the actual sensor is laying up against the plastic housing of the TMAP sensor body (verified our other shop car has the same issue) and it is shrouded by plastic fins.
This is bad because the intake manifold and sensor housing heat up to that 170F (sometimes hotter) and that heat gets transferred into the sensor. Even if the actual air temp is 100F, the sensor will be affected from touching something that is much hotter. Add the fact that plastic maintains heat for a long period of time, and you get very inaccurate readings. Going further, add the typical oil from blow by that accumulates on the sensor and it transfers even more heat. It does make for very consistent readings, but they are not a representative of what the actual air temp entering the engine is. This was verified by using the data we get from KTuner and using a laser temp probe to measure the surface of the sensor and the intake manifold. All of which read the same temp after the run was over and after the cool down.
An example is after a dyno run, we were seeing 150F ACT reading on the software, and with the laser probe. Revving up the motor to 4000RPM showed the temp hover around 145F, when this should have shown more like 100F. I saw the problem, only question is, can it be fixed and will it even do anything?
The Fix/How-To
I set off to fix this by trimming off the shroud in the center of the sensor. In the picture above you can see i outline the small center rectangle showing the center shroud. I used an X-acto knife and very carefully sliced it off as far down as I could. Then using a small flathead screw driver I bent the probe carefully toward the middle until it no longer touches anything (You will need to push it from part way down the probe as it will just spring back if you push from the top of it). After it was all done, the sensor was resting in the air not touching anything and still protected by some of the plastic housing. This took a whole 5 minutes of work with an X-acto knife. Below is what it looks like after it has been modified.
Results
Does fixing this actually do anything? Absolutely! First and foremost, there was an increase in power! Since the ECU uses charge temps and intake temps to control torque (boost and other things) it actually added power! Just to give you some idea, we were seeing consistently 300WHP before this mod (OEM intercooler, 3” Catback with overpipe, and Ktuner). After the fix, the HP jumped up 20WHP, and we saw the air temp recovery time change much faster and our laser probe measured the same 150-160F on the sensor and manifold, while the ECU was seeing 130F. Only downside was now that the ECU was reading a more accurate temperatures, we were now seeing a fluctuation in power. See the below graph showing the grouping of the runs.
It is hard to see but before the mod the HP was consistently low (grouping within smaller circle). After the mod the HP jumped up and stayed up a bit longer, but eventually did fall down to about 300WHP. Keep in mind that these tests were done on our dyno where things are very consistent, and we don’t have fans that can replicate road speed. This tends to lean to slightly worse conditions where there isn’t the same cooling as found on the street. Our testing methods can get close to track like conditions as we can replicate the same higher coolant temps people see on the track, but don’t see on the road.
And all dyno runs we have shown and will show, will be done with this ACT mod. I think it’s important for the consistency and accuracy of data.
The question is, does your car have this same problem? Does this apply to all the non-Type-R turbo models? We are not 100% sure at this point, but since we have now seen this on 4 cars, my guess is most Type-R’s have this issue. I would love to hear from people and see if their sensor is the same way.
WARNING: There is some added risk that this mod could cause the sensor to fail. Please mod at your own risk!
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